Breather for an internal combustion engine fuel tank

ABSTRACT

A breather valve for a gas tank of an internal combustion engine having an adsorption filter which is linked to the atmosphere by a breather line which is controlled by a shut-off valve. As air flows through the shut off valve, contaminations entrained in the shut off valve may deposit in the shut-off valve, so that it will no longer close tightly. For this reason, a particle filter has been arranged in front of the shut-off valve. The particle filter is of a large surface area which is integrated in the housing of the adsorption filter, thus contamination of the shut-off valve (51) and an excessive pressure drop of the air flowing through the particle filter (41) is avoided. The integrated construction facilitates a simple assembly of the adsorption filter (41) which is suitable for internal combustion engines in motor vehicles.

PRIOR ART

The invention is based on a breather for an internal combustion enginefuel tank. Such a breather with an adsorption filter, an active carbonfilter for example, is known (U.S. Pat. Nos. 4,175,526, 4,862,856),which prevents the escape of fuel vapours from a fuel tank into theatmosphere. The fuel vapours arise as soon as the fuel exceeds thesaturation temperature which is dependent on the ambient pressure.Initially, those parts of the fuel will evaporate which have the lowestsaturation temperature. With increasing fuel temperature or reducingambient pressure, the rate of fuel evaporation increases. The fuelvapour represents a severe pollution of the environment and a healthhazard for people, in particular when it is inhaled.

The adsorption filter is connected to the fuel tank by means of a filterline which terminates in the interior of the adsorption filter, forexample in that region which is filled with activated carbon. A suctionline which is controlled by a tank breather valve, links the adsorptionfilter with that part of the induction manifold of the internalcombustion engine which is downstream from a throttle.

With the engine running, the fuel vapour is drawn in by the vacuum whichexists in the induction manifold behind the throttle, and is fed to theengine, for combustion. At periods of rest or when the tank breathervalve is closed, or when the vacuum being accumulated in the inductionmanifold is insufficient due to the load conditions of the engine toallow the fuel vapour to be exhausted, the vapour is adsorbed in theadsorption filter.

The limited design space of the adsorption filter provides for a limitedstorage capacity. For regeneration, the adsorption filter is flushedwith fresh air which is fed to the filter via a breather line which islinked to the atmosphere. With negative pressure prevailing in theinduction manifold and the tank breather valve open, the fresh air willpass first through a shut-off valve, which controls the breather line,into the adsorption filter, where it absorbs the fuel vapour and feedsit through the suction line and the induction manifold, to the engine.

With both the shut-off valve and the tank breather valve closed, it isrequired for reasons of function and environment protection, that thefuel tank, the filter line, and the adsorption filter form a single unitwhich is hermetically sealed from the atmosphere. To check the sealingefficiency, a negative pressure is set in this unit (see DE-OS 40 03751). If one of the components is leaky, the negative pressure cannot bemaintained, since air from the outside will flow into this unit.Following this leak diagnosis, the shut-off valve is opened, and withthe tank breather valve open, fresh air will flow via the shut-off valveinto the adsorption filter, regenerating the adsorption filter, and isthen fed as a mixture to the engine.

With such a shut-off valve, there is the risk that condensate willaccumulate in its electrical region and cause faults or failure of theshut-off valve.

Furthermore, with such a shut-off valve, there is the risk that anyfault in the electromagnetic circuit will unintentionally keep the valveclosed and that, with the tank breather valve closed, an inadmissiblyhigh pressure will build up in the fuel tank, the lines, and theadsorption filter, causing faults. The fresh air flowing into theadsorption filter contains impurities, for example in the form of dustand dirt particles. These impurities will partly deposit in the interiorof the shut-off valve, for example, on the sealing faces of a valveclosing body and the valve seat. When the valve closes again, thedeposited impurities will prevent repeated tight closing of the shut-offvalve. If the unit is to be subjected to a further leak test, air willenter into the unit from outside through the defective shut-off valvewhich has negative pressure. This makes it impossible to positivelyassess whether the leak stems from a possibly existing leak somewhere inthe unit or from insufficient sealing of the shut-off valve.

In known breathing devices (U.S. Pat. Nos. 4,1 75, 526, 4,8 62, 856), asmall particle filter is provided, extending in a radial direction,between the shut-off valve and the atmosphere, which is of very fineporous construction in order to retain even the smallest dirt particles.This results in a very high pneumatic flow resistance of the particlefilter, with the disadvantage that the regenerating air flow encountersan undesirably high pressure drop at the particle filter, which causes anegative pressure in the adsorption filter. This negative pressure willalso take effect in the fuel tank where it causes an unintendedintensified evaporation of the fuel. A further disadvantage is the factthat during filling of the fuel tank, the vapour which has formed ispushed towards the adsorption filter, with the shut-off valve open, andthat the pressure drops at the particle filter, which triggers theshut-off mechanism of the fuel hose nozzle in an undesirable manner.

ADVANTAGES OF THE INVENTION

In contrast, the breather in accordance with the invention for aninternal combustion engine fuel tank has the advantage thatnotwithstanding the use of a fine porous particle filter, it is ensuredthat only a negligible negative pressure is created in the adsorptionfilter by the particle filter. The large flow cross-section of theparticle filter reduces the pressure drop of the medium which flowsthrough the particle filter. Moreover, the particle filter has a longerlife due to the large surface area.

The measures listed herein facilitate advantageous developments andimprovements of the breather specified in the main claim.

The breather line, which extends at least partially outside theadsorption filter, enables simple mounting of the shut-off valve and ofthe breather line. The electrical connections required for the controldo not have to be routed through housing apertures which are sealed tothe environment.

A further advantage is the design and arrangement of the shutoff valvein a manner which allows any condensate which forms to flow off withoutimpairing the function of the shut-off valve.

It is a further advantage if the magnetic circuit of the shut-off valveis designed so that at a predetermined pressure in the fuel tank, theshut-off valve is forced in opposition to the magnetic force.

Due to the arrangement of at least one baffle in the adsorption filter,a more intense and prolonged through-flow of the adsorption medium ismade possible in an advantageous manner.

BRIEF DESCRIPTION OF THE DRAWING

Embodiment examples of the invention are shown simplified in the drawingand are more closely explained in the description which follows.

FIG. 1 shows a first example of a breather in accordance with theinvention,

FIG. 2 shows a second embodiment example of a breather, in part, whichis designed in accordance with the invention,

FIG. 3 shows a third embodiment example of a breather, in part, which isdesigned in accordance with the invention.

DESCRIPTION OF THE EMBODIMENT EXAMPLES

FIG. 1 shows a diagrammatic view of a breather of an internal combustionengine, for example for a motor vehicle. The breather includes anadsorption filter 1, a fuel tank 2, and a tank breather valve 3. Thefuel tank 2 is filled via a filler neck 6 which is closed by a tank cap7. The adsorption filter 1 and the fuel tank 2 are connected to eachother via a filter line 8 which starts from a region of the fuel tank 2in which the vapour-like proportions of the fuel will mainly collect.

At the interphase layer between the liquid and vapour-like fuel,represented by a triangle, the liquid phase changes into the vapourphase at the values which correspond to the vapour pressure curve, andenriches the space above the liquid phase with fuel vapour. A commercialfuel for a known mixture compressing, spark ignited internal combustionengine, for example, may contain proportions whose saturationtemperature lies below 40° C., which therefore will have completelyevaporated at a fuel temperature of 40° C. The vapour pressure of thefuel corresponds to the sum total of the partial pressures of thevapour-like proportions of the fuel. At a fuel temperature of 40° C.,for example, the vapour pressure of a fuel being used for a knownmixture compressing spark ignited internal combustion engine can reachvalues of up to 1.9 bar, i.e. above the standard pressure of approx.1.013 bar. With a rising temperature or reducing ambient pressure, therate of evaporation will increase up to the point where a state ofequilibrium is once again achieved.

A suction line 16, which is controlled by the tank breather valve 3,links the adsorption filter 1 to an induction manifold 3 of the engine,which is not shown. The suction line 16 terminates in an inductionmanifold 13 in a section downstream from a throttle 18, in whichnegative pressure prevails, conditioned by the load.

The end of the suction line 16 which faces the adsorption filter coupleswith a suction line connection 20 of a disc-shaped housing cover 21which covers a corresponding cylindrical housing 22 of the adsorptionfilter 1 at its one end. The housing cover 21 is tightly connected tothe housing 22 and the suction line 16. Inside the housing 22, a firstgas permeable filter insert 23 which extends at an axial separation fromthe housing cover 21 and over the entire inner cross-sectional area ofthe housing 22 at right angles to the longitudinal axis 19 of thehousing, is arranged. An annular housing section 24 of the housing 22,the housing cover 21, and the filter insert 23, define a first reservoir26 which, by means of the suction line connection 20, is linked to thesuction line 16, and, when the tank breather valve 3 is open, to theinduction manifold 13.

On the face of the first filter insert 23, facing away from the housingcover 21, a second filter insert 27, at an axial separation from thefirst filter insert, covers the entire inner cross-section of thehousing 22 of the adsorption filter 1. An annular housing section 25 ofthe housing 22, the first filter insert 23, and the second filter insert27, define an adsorption chamber 28 which is completely or partly filledwith an adsorption medium 31, activated carbon for example. Theadsorption chamber 28 is linked to the first reservoir 26 by means ofthe gas permeable first filter insert 23.

The filter line 8 which links the fuel tank 2 with the adsorption filter1 is passed through the housing cover 21 by means of filter connection32 and is tightly connected to the housing cover 21. The first stowagechamber 26 is penetrated through its entire axial extent by the filterline 8. In the further progression, the filter line 8 penetrates thefirst filter insert 23 through an aperture 33 and terminates, forexample, in the adsorption chamber 28 which is filled with activatedcarbon. The fuel tank 2 and the adsorption chamber 28 are thus directlylinked by the filter line 8.

A gastight dividing wall 36 penetrates the inner cross-section of thehousing 22 on that face of the second filter insert 27 which faces awayfrom the adsorption chamber 28, and is closely connected with thehousing 22. A second reservoir 37 is defined by a housing section 29 ofthe housing 22, the second filter insert 27, and the dividing wall 36.The first reservoir 26, the adsorption chamber 28, and the secondreservoir 37 are connected with one another by the first filter insert23 and the second filter insert 27 in a manner to allow gas permeance.

The dividing wall 36 and an annular end section 30 of the housing 22form a pot shaped filter chamber 38, open to the atmosphere, which iscompletely covered by a fine porous particle filter 41 at the endopposite the dividing wall 36. The particle filter 41 thus extends overthe entire inner cross-section of the housing 22 and separates thefilter chamber 38 from the atmosphere in a manner to allow gaspermeance, and is able to filter out the finest dirt particles from theatmosphere. An inner wall 39 encloses the inner cross-section of thehousing 22 so that the particle filter 41 extends at least over theclearance width of the housing 22 which is defined by the inner wall 39.The particle filter 41 is thus designed with a large area transverse tothe flow of the regenerating air, thereby effecting only a minorpressure drop of below 5 mbar in an air flow of approximately 3 m³ /h.The housing cover 21, the housing 22, and the dividing wall 36 form aclosed space which is linked to the outside by virtue of the suctionline connection 20, the filter line connection 32, and a first breatherline connection 42. The housing 22 has a second breather line connection45, open to the filter chamber 38, which has the same angle coordinatewith regard to the cylindrical housing 22 as the first breather lineconnection 42. One end each of a `U` shaped breather line 46 is tightlyinserted into the breather line connections 42, 45, so that the filterchamber 38 and the second reservoir 37 are linked to each other. Thebreather line 46 is sealed to the housing 22 by means of elastic sealingelements 47, 48, e.g. `O` rings.

A shut-off valve 51, for example an electromagnetically operated valve,controls the breather line 46. In this arrangement, an upper short feedpipe 52 of the shut-off valve 51, which is inserted into the firstbreather line connection 42, and a lower short feed pipe 53 of theshut-off valve, which is inserted into the second breather lineconnection 45, form sections of the breather line 46. To avoid pressure,which has been generated by fuel vapour due to inadvertent or faultyclosure of the tank breather valve 3 and the shut-off valve 51, burstingopen the fuel tank 2, the filter line 8, the suction line 16 or thehousing 22 of the adsorption filter 1, it must be possible to force openthe shut-off valve 51 by pressure. For this purpose, the magneticcircuit 54 of the shut-off valve 51 must be designed so that at apredetermined pressure in the adsorption filter 1, for example 0.3 bar,the pressure which thereby acts on a valve closing part 55--which onexcitation of the magnetic circuit 54 is moved into the closing positionof the shut-off valve 51--is sufficient to move the valve closing part55, in opposition to the magnetic force, into the opening position ofthe shut-off valve. Thus, the shut-off valve 51, as shown in FIG. 1, maybe designed with a valve closing part 55, which in the non-energizedstate of the magnetic circuit 54 is moved by a return spring 49 into theopening position in the direction towards the lower short feed pipe 53,which is connected with the filter chamber 38, i.e. lifted off a valveseat 50 which lies in the direction of the upper short feed pipe 52.When the magnetic circuit 54 is energized, the valve closing part 55 ispushed to the valve seat 50 in the direction towards the upper shortfeed pipe 52 with just sufficient force to allow a force generated by apressure of approximately 0.3 bar in the adsorption filter 1, to movethe valve closing part 55 in opposition to the magnetic force, away fromthe valve seat 50 in the direction to the lower short feed pipe 53. Thenow open shut-off valve 51 allows the pressure in the adsorption filter1 and in the fuel tank 2 to be reduced. The shut-off valve 51 can bedesigned, in a manner not shown, with a valve closing part which in theenergized state of the magnetic circuit can be moved in opposition tothe force of a return spring in the direction from the upper short feedpipe 52 to the lower short feed pipe 53, during which action it willcome to rest on the valve seat until a force in the adsorption filter,generated by a pressure of approximately 0.3 bar, which impinges on thevalve closing part, lifts the valve closing part, in opposition to themagnetic force, off the valve seat and facilitates a pressure relief asdescribed above. In the non-energized state of the magnetic circuit, thevalve closing part is moved by the return spring in the direction oftile upper short feed pipe 52, i.e. away from the valve seat, into theopening position of the shut-off valve.

In the dashed line representation in FIG. 1, a shut-off valve 51' isalso shown, which is arranged within the filter chamber 38 which isidentical to the shut-off valve 51 in terms of function and structure.The breather connections 42 and 45 in the housing are closed. Thebreather connection 42' penetrates the dividing wall 36 and is connectedto the obliquely upwards extending upper short feed pipe 52' of theshut-off valve 51'. A lower short feed pipe can be dispensed with in theshut-off valve 51', since the vertically arranged shut-off valve 51' canbe open to the bottom in the direction of the particle filter 41. Theshut-off valve 51 thus takes on the additional function of a safetyvalve.

The shut-off valve 51 is open in the non-energized state in order toavoid a pressure rise in the fuel tank 2 in the event of power failure,for example after an accident. Opening of the shut-off valve 51 in thenon-energized state is accomplished in the known manner, for example bythe return spring 49.

In order to prevent condensate entering into the live components, e.g.in a magnetic circuit 54 with magnetic coil and core of the shut-offvalve 51, the shut-off valve 51 is aligned such that the magneticcircuit 54 is arranged at the highest gravitational point of theshut-off valve 51. The discharge of condensate from the reservoir 37,the breather line 46, and the shutoff valve 51 in the direction of theatmosphere, is enhanced by virtue of the fact that the valve closingpart 55 performs a vertical opening and closing movement along avertical axis 56 and that the valve seat 50 is concentric with thisvertical axis 56. The magnetic circuit 54 then lies above the valve seat50 and also above the upper short feed pipe 52, or above the air routein the shut-off valve 51 from the upper short feed pipe 52 to the valveseat 50. A downward incline of the short feed pipes 52 and 53, as shownfor the upper short feed pipe 52' of the shut-off valve 51',additionally enhances the condensate discharge.

If portions of the fuel evaporate, they pass through the filter line 8into the adsorption chamber 28 of the adsorption filter 1 from wherethey are drawn off through the suction line 16 into the manifold 13,with the tank breather valve 3 open, due to the load dependent negativepressure which prevails in the induction manifold 13 of the runningengine, and are fed to the internal combustion engine for burning. Withthe tank breather valve 3 closed, or in the event of an insufficientnegative pressure in the induction manifold 13, the fuel vapour whichescapes from the fuel tank 2 are stored by the activated carbon in theadsorption chamber 28 of the adsorption filter 1. When the tank breathervalve 3 is again opened or when the pressure in the induction manifold13 reduces, fresh air is drawn from the atmosphere via the particlefilter 41, through the adsorption filter 1, and regenerates theactivated carbon in the adsorption chamber 28 of the adsorptionfilter 1. The portion of the fuel vapour which is retained in theactivated carbon is taken up and fed through the suction line 16 to theengine, for burning.

In order to prevent contamination of the adsorption filter 1, inparticular of the shut-off valve 51, the air which flows from theatmosphere into the adsorption filter 1, is first purged of anyimpurities, such as dust, by the particle filter 41. Due to the particlefilter 41, the fresh air flow encounters a pressure drop whichpropagates as negative pressure directly into the fuel tank where itunintentionally increases the rate of fuel evaporation. In order tofurther reduce the emission of fuel vapour, a fuel hose nozzle whichseals against the filler neck 6 can be used for filling. In this case,the fuel vapour is displaced by the adsorption filter 1 and causes,among other things, a pressure drop at the particle filter 41, whichleads to a pressure rise at the fuel hose nozzle which on reaching adefinite value, unintentionally triggers the automatic shut-offmechanism of the filler nozzle.

In addition to the pore size, the cross-sectional area of the particlefilter 41 decisively influences the pressure drop caused on the particlefilter 41. In order to achieve an adequate purification of the fresh airdrawn in, a very small pore size must be selected, i.e. a small-poreparticle filter 41, which causes the pressure drop to considerablyintensify.

This undesirable side effect can be compensated for by a largecross-sectional area, so that the risk of an unintentional triggering ofthe shut-off mechanism of the filler nozzle, and the increase in therate of evaporation of the fuel in the fuel tank 2 is reduced. Theparticle filter 41 thereby obtains a large cross-sectional area with apressure drop of an acceptable size, so that the particle filter 41extends at least over the entire inner cross-section of the housing 22.

In order to check the sealing efficiency of the breather, the shut-offvalve 51 or 51' is closed. Due to the negative pressure which exists inthe induction manifold, a negative pressure will occur in the fuel tank2, the filter line 8, the adsorption filter 1, and the suction line 16.The tank breather valve 3 is then closed.

If the fuel tank 2, the filter line 8, the adsorption filter 1, thesuction line 16, the tank breather valve 3, and the shut-off valve 51 or51', and all connections of the above named component are free from anyleak, the negative pressure will be maintained. The pressure isascertained by a pressure sensor 80, which is arranged for example onthe adsorption filter 1 and projects into one of the chambers 26, 28, or37. The pressure sensor 80, the tank breather valve 3, and the shut-offvalve 51 or 51' are connected to an electronic control unit 81. If thereis a leak in one of these components or in a connection, then air willflow in the direction of the negative pressure regions and causepressure compensation, so that the negative pressure can be maintainedonly over a short period and the pressure sensor 80 transmits a varyingsignal to the control unit 81.

Of particular importance in this context is tight closing of both theshut-off valve 51 and of the tank breather valve 3. Should one of thenamed valves fail to close completely, air will enter into the shut-offchamber via the leaking valve. It is then no longer possible to statewith confidence to what extent the system has become leaky or whether-the air is entering through an insufficiently closing valve. Theshut-off valve 51, through which the fresh air, which regenerates theadsorption filter 1, flows first, is particularly susceptible. It ishere that there is a particularly high risk that contaminations of theair will deposit in the shut-off valve 51 and prevent a completely tightclosure. The particle filter 41, which has a large area, is integratedin the housing 22 and covers the inner cross-section, preventscontamination of the shut-off valve 51, without impairing the generalfunction of the breather due to an excessive pressure drop of the freshair which flows through it.

Instead of being arranged somewhere in the suction line 16, the tankbreather valve may alternatively be arranged at the start of the suctionline 16, i.e. directly on or in the adsorption filter 1, as shown by thetank breather valve 3' represented by a dashed line. The arrangement ofindividual or of all components, such as shut-off valve, tank breathervalve, pressure sensor, and particle filter on or in the adsorptionfilter provides a very compact assembly which only requires to beconnected to the fuel tank and the induction manifold on the motorvehicle.

FIGS. 2 and 3 show two further embodiment examples of a breatherdesigned in accordance with the invention, with an adsorption filter fora fuel tank, in which the tank, the tank breather valve, and theinduction manifold have been omitted. Components which are identical inrelation to the embodiment example in FIG. 1 and which are of identicalaction are identified by the same reference symbols. The adsorptionfilter 1 shown in FIG. 2 has a first reservoir 26 which is separatedfrom the adsorption chamber 28 by the first filter insert 23, and asecond reservoir 37 which, differing from the embodiment example shownin FIG. 1, is separated from the adsorption chamber 28 which is at leastpartly filled with the adsorption medium 31, by the second filter insert27 and a first baffle 60. The second reservoir extends only partiallyover the entire inner cross-section of the housing 22. For thisarrangement, the first baffle 60, starting from the dividing wall 36,extends for example in the longitudinal direction of the inner wall 39of the housing 22 and vertically in relation to the dividing wall 36,partly into the adsorption chamber 28, and terminates with a separationfrom the first filter insert 23, so that between the first baffle 60 andthe first filter insert 23, a free cross-section remains. The firstbaffle 60 then is at a small separation from the right inner wall 39,for example, of the housing 22.

At a lateral separation from the first baffle 60, away from theright-hand inner wall 39 and starting from the housing cover 21, forexample at right angles to the housing cover 21, a second baffle 61projects partly into the adsorption chamber 28, at least as far as intothe adsorption medium 31. A cross-section remains free between that endof the second baffle 61 which faces the dividing wall 36. Two parallelbaffles 60, 61 divide the adsorption chamber 28 into three chambers, twoof which, namely 57, 58 are of approximately equal size, and one, 59, issmaller by the volume of the reservoir 37, these chambers areinterconnected by the cross-sections which remain free between the firstbaffle 60 and the first filter insert 23 and the second baffle 61 andthe dividing wall 36. The smaller right-hand chamber 59 is connected tothe first reservoir 26 so as to permit gas permeance, by means of thefirst filter insert 23, and to the second reservoir 37 by means of thesecond filter insert 27.

The suction line connection 20 and the filter line connection 32 arearranged in that region of the housing cover 21 which partly defines theleft-hand chamber 57, so that the maximum distance possible lies betweenthe entry of the fresh air at the second filter insert 27 and thesuction line connection 20, thus providing air flow around much of theadsorption medium 31.

The shut-off valve 51 already described for the embodiment example inFIG. 1 is inserted with the short feed pipes 52 and 53 into the breatherline connections 42 and 45 in the manner described there, so that aconnection can be made between the filter chamber 38, which is definedby the large area particle filter 41, and the second reservoir 37.

Deviating from the adsorption filter in the FIGS. 1 and 2, the housing22 of the adsorption filter 1 in accordance with FIG. 3 has a lateralrecess 62, which is of such a size as to accommodate the shut-off valve51 and the vent line 46, without projecting beyond the outline of thehousing 22. In a longitudinal wall 65 of the recess 62, which isparallel to the inner wall 39 of the housing 22, two breather lineconnections 42 to the second reservoir 37 and 45 to the filter chamber38 are arranged, into which the short feed pipes 52 and 53 of thebreather line 46 are inserted. Arranged between the dividing wall 36 andthe first filter insert 23 and extending parallel with these is a lowerbaffle 63, which starts from the inner wall 39 at the recess 62 andprojects into the adsorption chamber 28 with a separation from the firstfilter insert 23. This baffle does not, however, extend over the entirecross-section of the housing 22 up to the opposite inner wall 39. Across-section remains free between the end of the lower baffle 63, whichlies in the adsorption chamber 28, and the inner wall 39 of the housing22.

The lower baffle 63 divides the adsorption chamber 28 into a lowerchamber 67 at the dividing wall 36 and an upper chamber 68 at the firstfilter insert 23. The second filter insert 27 is arranged with a lateralseparation from the longitudinal wall 65 of the recess 62 between thelower baffle 63 and the dividing wall 36; the filter insert 27, togetherwith this dividing wall 36, the lower baffle 63, and the housing 22,defines the second reservoir 37. An upper baffle 64 extends from thehousing cover 21 and projects partly into the adsorption chamber 28,certainly at least into the adsorption medium 31, and divides the upperchamber 68 into a left-hand chamber 69 and a right-hand chamber 70. Thesuction line connection 20 and the filter line connection 32 arearranged in that region of the housing cover 21 which lies above theright-hand chamber 70. The upper baffle 64 terminates above the lowerbaffle 63, leaving a vertical free cross-section between the upperbaffle 64 and the lower baffle 63, via which a gas exchange can takeplace between the chambers 69 and 70. In this way, the maximum pathlength is achieved and air flow around much of the adsorption medium 31is ensured between the entry of fresh air into the second reservoir 37and the suction line connection 20. The shut-off valve 51, inserted intothe breather line connections 42 and 45 of the recess 62 by means of theshort feed pipes 52 and 53, is enclosed in the contour of the housing 22and is thus better protected from damage.

The foregoing relates to a preferred exemplary embodiment of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

We claim:
 1. A breather for a fuel tank of an internal combustion enginehaving an adsorption filter comprising an adsorption chamber (28), anadsorption medium (31) contained within said adsorption chamber and ahousing which is linked by means of a suction line to an inductionmanifold of the internal combustion engine and, by means of a filterline to the fuel tank and to a breather line to the atmosphere which canbe shut off by a shut-off valve (51) in a breather line, and wherein aparticle filter is arranged between the atmosphere and the shut-offvalve, the particle filter (41) forms an outer wall of the housing (22)of the adsorption filter (1) thereby forming a filter chamber (38)between said particle filter and a gas tight dividing wall (36), saidgas tight dividing wall (36) separates said filter chamber (38) fromsaid adsorption chamber, said particle filter links said filter chamberwith the atmosphere in a manner to allow gas permanence and is designedwith a large surface area, so that the particle filter causes only aminor pressure drop in the adsorption filter (1) and the gas passesthrough the particle filter, and the said filter chamber, said shut-offvalve (51), and said adsorption chamber (28) which are connected in agas flow path.
 2. A device in accordance with claim 1, in which theparticle filter (41) extends over an inner cross-section of the housing(22) which extends at right angles to a longitudinal axis (19) of thehousing.
 3. A device in accordance with claim 1, in which the filterchamber (38) is separated by the gas tight dividing wall (36) from areservoir (37) which is connected to the adsorption chamber (28) in thehousing (22) which accommodates the adsorption medium (31), and that thefilter chamber (38) is connected to the reservoir (37) by means of thebreather line (46).
 4. A device in accordance with claim 2, in which thefilter chamber (38) is separated by the dividing wall (36) from areservoir (37) which is connected to the adsorption chamber (28) in thehousing (22) which accommodates the adsorption medium (31), and that thefilter chamber (38) is connected to the reservoir (37) by means of thebreather line (46).
 5. A device in accordance with claim 1, in which thedividing wall (36) separates the filter chamber (38) from the adsorptionchamber (28), which accommodates the adsorption medium (31), in thehousing (22) and is linked to the adsorption chamber by means of thebreather line (46).
 6. A device in accordance with claim 2, in which thedividing wall (36) separates the filter chamber (38) from the adsorptionchamber (28), which accommodates the adsorption medium (31), in thehousing (22) and is linked to the absorption chamber by means of thebreather line (46).
 7. A device in accordance with claim 3, in which thebreather line (46) extends at least partly outside the housing (22) andthat the shut-off valve (51) is arranged outside the housing (22).
 8. Adevice in accordance with claim 5, in which the breather line (46)extends at least partly outside the housing (22) and that the shut-offvalve (51) is arranged outside the housing (22).
 9. A device inaccordance with claim 7, in which the shut-off valve (51) is arranged ina recess (62) of the housing (22).
 10. A device in accordance with claim8, in which the shut-off valve (51) is arranged in a recess (62) of thehousing (22).
 11. A device in accordance with claim 7, in which theshut-off valve (51) forms a compact assembly with the housing (22) ofthe adsorption filter (1).
 12. A device in accordance with claim 8, inwhich the shut-off valve (51) forms a compact assembly with the housing(22) of the adsorption filter (1).
 13. A device in accordance with claim11, in which the shut-off valve (51) can be inserted, gastight, by meansof short feed pipes (52, 53) into breather line connections (42), 45) ofthe housing (22).
 14. A device in accordance with claim 12, in which theshut-off valve (51) can be inserted, gastight, by means of short feedpipes (52, 53) into breather line connections (42), 45) of the housing(22).
 15. A device in accordance with claim 1, in which the shut-offvalve (51, 51') is provided with a magnetic circuit (54) which, whenenergized, moves a valve closing body (55) into a closing position andwhich is designed to be only of such power that above a certain pressurein the adsorption filter (1), the force produced hereby is sufficient tomove the valve closing body (55) into the opening position.
 16. A devicein accordance with claim 1, in which the shut-off valve (51, 51') has avertical axis (56) and that a valve closing part (55) of the shut-offvalve (51, 51') is arranged to be movable along the vertical axis (56),so that any condensate which may form can readily flow off downward whenthe valve closing body (55) has lifted off its seat (50).
 17. A devicein accordance with claim 16, in which the shut-off valve (51, 51') isoperated by means of a magnetic circuit (54) and that the magneticcircuit (54) is arranged above an air path by means of the shut-offvalve (51, 51').
 18. A device in accordance with claim 16, in which theshut-off valve (51,51') has short feed pipes (52, 53) for supplying airor discharging it, and that at least one of the short feed pipes (52,53) extends at an incline.
 19. A device in accordance with claim 17, inwhich the shut-off valve (51,51') has short feed pipes (52, 53) forsupplying air or discharging it, and that at least one of the short feedpipes (52, 53) extends at an incline.
 20. A device in accordance withclaim 3, in which the adsorption chamber (28) is divided into chambers(57, 58, 59; 67, 68, 69, 70) by at least one baffle (60, 61; 63, 64)which deflects the air flow.
 21. A device in accordance with claim 5, inwhich the adsorption chamber (28) is divided into chambers (57, 58, 59;67, 68, 69, 70) by at least one baffle (60, 61; 63, 64) which deflectsthe air flow.
 22. A device in accordance with claim 1, in which a sensor(80) is arranged relative to the adsorption filter (1).
 23. A device inaccordance with claim 1, in which a tank breather valve (3) for thecontrol of the suction line (16) is arranged relative to the adsorptionfilter (1).